Patch "dm-verity, dm-crypt: align "struct bvec_iter" correctly" has been added to the 4.19-stable tree

Patch "dm-verity, dm-crypt: align "struct bvec_iter" correctly" has been added to the 4.19-stable tree

[Sasha Levin]

This is a note to let you know that I've just added the patch titled

    dm-verity, dm-crypt: align "struct bvec_iter" correctly

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-verity-dm-crypt-align-struct-bvec_iter-correctly.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.



commit c048b053cf419f832c332a213fe4c3438cf2f192
Author: Mikulas Patocka <mpatocka@redhat.com>
Date:   Tue Feb 20 19:11:51 2024 +0100

    dm-verity, dm-crypt: align "struct bvec_iter" correctly
    
    [ Upstream commit 787f1b2800464aa277236a66eb3c279535edd460 ]
    
    "struct bvec_iter" is defined with the __packed attribute, so it is
    aligned on a single byte. On X86 (and on other architectures that support
    unaligned addresses in hardware), "struct bvec_iter" is accessed using the
    8-byte and 4-byte memory instructions, however these instructions are less
    efficient if they operate on unaligned addresses.
    
    (on RISC machines that don't have unaligned access in hardware, GCC
    generates byte-by-byte accesses that are very inefficient - see [1])
    
    This commit reorders the entries in "struct dm_verity_io" and "struct
    convert_context", so that "struct bvec_iter" is aligned on 8 bytes.
    
    [1] https://lore.kernel.org/all/ZcLuWUNRZadJr0tQ@fedora/T/
    
    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Signed-off-by: Mike Snitzer <snitzer@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 569904f73994a..95ed46930a90e 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -46,11 +46,11 @@
 struct convert_context {
 	struct completion restart;
 	struct bio *bio_in;
-	struct bio *bio_out;
 	struct bvec_iter iter_in;
+	struct bio *bio_out;
 	struct bvec_iter iter_out;
-	u64 cc_sector;
 	atomic_t cc_pending;
+	u64 cc_sector;
 	union {
 		struct skcipher_request *req;
 		struct aead_request *req_aead;
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index 6e65ec0e627a6..04ef89e318564 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -72,11 +72,11 @@ struct dm_verity_io {
 	/* original value of bio->bi_end_io */
 	bio_end_io_t *orig_bi_end_io;
 
+	struct bvec_iter iter;
+
 	sector_t block;
 	unsigned n_blocks;
 
-	struct bvec_iter iter;
-
 	struct work_struct work;
 
 	/*